Final answer:
The CPA's best defense against a common law fraud accusation by a stockholder is generally that the auditor followed GAAS. This demonstrates that the auditor carried out the audit according to professional standards, thus showing no intent to deceive. Other defenses like contributory negligence or lack of privity are typically considered secondary.
Step-by-step explanation:
If a stockholder sues a CPA for common law fraud based on false statements contained in the financial statements audited by the CPA, the CPA's best defense would typically be that the auditor followed GAAS (Generally Accepted Auditing Standards). This defense suggests that the CPA performed the audit according to professional standards, which is a critical factor in proving that the auditor conducted the work competently and without intent to deceive or commit fraud. It implies that any inaccuracies in the financial statements were not due to the auditor's neglect or misconduct.
Contributory negligence of the client or the fact that the CPA did not financially benefit from the alleged fraud could potentially support the CPA's case, but these would likely be secondary arguments. Privity of contract between the stockholder and the CPA also might not offer a strong defense, particularly if the jurisdiction recognizes third party rights to sue for negligence. Therefore, adherence to GAAS stands as the most robust defense for an auditor in a fraud accusation.